This application claims the priority of application 1997 2959/97, filed in Switzerland on Dec. 23, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a gear pump and a method for positioning a gear pump shaft.
Gear pumps of the simplest design consist of a pair of gears that are the same size and mesh with one another, said gears being surrounded on all sides by a housing. The gears are mounted on two shafts mounted in the housing, one of said shafts, once again the simplest design, being guided to the outside through a shaft seal as a drive shaft. On both sides of the tooth engagement, the housing has an opening for admitting and discharging the pumping medium. When the gears rotate, the tooth spaces that disengage fill with the pumping medium flowing in, which is then delivered to the pressure side along the housing walls. At that point, it is compressed by the teeth which then again engage in the spaces, compressing the medium, and forcing it through the outlet opening into a pressure line.
Gear pumps represent proven pressure-developing systems with a high volumetric efficiency. Therefore, the forces acting on the gears and thus on the shafts carrying the gears are correspondingly high and must be accepted in known fashion by corresponding slide bearings. The slide bearings are traversed by the pumping medium and lubricated thereby. According to bearing theory, the shafts float in the bearings when the operating conditions are correctly chosen, so that the bearing load and the bearing carrying capacity are in equilibrium.
A known gear pump is described for example in patent publication EP-0 753 678.
However, the known design for gear pumps suffers from the disadvantage that these gear pumps depend on the rheological and thermal boundary values of the pumping medium. In other words gear pumps must be designed on the basis of the pumping medium.
The present invention therefore has a goal of providing a method and/or a gear pump in which the above mentioned disadvantages do not occur.
This goal is achieved according to preferred embodiments of the invention by producing an arrangement wherein the radial positioning of the gears takes place by means of the tooth tips and the interiors of the bores in the pump housing.
Advantageous embodiments of the invention including gear pumps and shaft positioning methods are described in the following specification and claims.
The invention has the following advantages: while the radial positioning of the gears is performed by the tooth tips and the insides of the housing bores, a decoupling of the operating conditions from the properties of the pumping medium is achieved, at least any residual attendance of the operating conditions on the flow behavior of the pumping medium is slight. Accordingly, the manufacturing costs for gear pumps according to the invention can be reduced significantly. Since the gears are supported over the entire width of the tooth, shaft deformations are completely eliminated in this new gear pump. This also includes the advantage that the play can be much smaller when the drive shaft passes through the shaft feedthrough.
In addition, the elimination of conventional slide bearings significantly reduces the number of parts required, reduces the housing dimensions, and simplifies the design of the housing overall. In this way, the axial play in particular is less than in known gear pumps, which means that a higher efficiency and hence lower losses are obtained with the gear pump according to the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.